Method and device for the automatic control of illumination devices

ABSTRACT

A method and a device are proposed for the automatic control of illumination devices ( 24 ), having a control element ( 22 ) which acts on illumination devices ( 24 ) and which is calibrated at time intervals (T), for which various calibration parameters are taken into account.

BACKGROUND INFORMATION

[0001] The present invention relates to a method and a device for theautomatic control of illumination devices, particularly of a motorvehicle, according to the species defined in the independent claims.Such methods are already known—for example, from the German Patent 19523 262—but they describe only how the external illumination devices arecontrollable on the basis of an absolutely incident quantity of light.However, an unwanted change in the control characteristic results due tovarious aging effects.

SUMMARY OF THE INVENTION

[0002] The method of the present invention having the features of themain claim has the advantage that the control element, which acts on theillumination devices, is calibrated at time intervals, therebypermitting compensation for aging effects of the optical media situatedin the sensing region.

[0003] A further advantage is yielded if the calibration parameters of arain sensor, which is likewise calibrated at time intervals, are relayedto the control element. The rain sensor and the control element forcontrolling illumination devices are frequently arranged in a singlehousing and have similar or even identical optical media. The result isthat the aging process of both optical media proceeds in a similar orreally identical manner.

[0004] The measures specified in the dependent claims yield advantageousfurther developments and improvements of the features indicated in themain claim.

[0005] It is advantageous if the rain sensor has a transmitter, areceiver and a light-conducting member; the receiver receives the lightconducted through the light-conducting member from the transmitter andcompares this signal to a setpoint value. In this way, the transmissionproperties are easily ascertainable, which means a simple calibration ofthe control element may be carried out.

[0006] A higher accuracy may be achieved if a transmittance isdetermined as result from the comparison of the received light signal tothe setpoint value, and the control element is calibrated with the aidof this transmittance, since it is substantially responsible for theshift of the operating point of the control element.

[0007] If the control element has a second light-conducting member whichis in correlation with the optical properties of the firstlight-conducting member, then this correlation may be taken into accountin the calibration of the control element. In this way, thelight-conducting member of the control element may be different from thelight-conducting member of the rain-sensor device, in particular may bemade of various plastics or glasses. Due to the correlation of theoptical properties, the control element may still be calibrated exactly.

[0008] If the correlation is stored as a functional cohesion in thecontrol element, any correlation as desired of the optical properties ofthe two light-conducting members may advantageously be taken intoaccount in the calibration, provided they are able to be representedfunctionally.

[0009] If the calibration is carried out with the aid of a correlationstored as a table in the control element, storage and computing power ofthe control element are minimized. The calibration can then be carriedout in a very simple manner without having to forfeit some of theflexibility of the correlation.

[0010] In addition, it is particularly advantageous to provide acalibration section over which a calibration parameter, which is takeninto account during the calibration, is determined at time intervals(I).

[0011] A very simple calibration may also advantageously be performed,in that it is only carried out as a function of time. Particularly inthe case of plastics, it is possible to proceed in this manner as arough approximation of the transmission change, which means no furthermeasuring distances are necessary.

[0012] A further beneficial calibration possibility is given if thecalibration is a function of the brightnesses measured during thehistory of the control element. The optical properties of many plasticschange as a function of time and the intensity of the light to which theplastics are exposed. If these variables are measured, with the aid ofempirical values, it is possible to draw conclusions about the opticalproperties of the plastic.

[0013] Moreover, it is advantageous to in each case construct thelight-conducting members and the electronics of the rain sensor and thecontrol element in one piece in order to save installation space andreduce costs.

[0014] The device of the present invention having the features of claim10 has the advantage that the control element is calibrated at timeintervals. It is thereby possible to compensate for aging effects of theoptical media, situated in the sensing region, or of the receivers. Inthis context, it is particularly advantageous if the calibrationparameters of a rain sensor are usable for calibrating the controlelement.

[0015] It is particularly advantageous if the rain sensor has atransmitter, a receiver and a light-conducting member, and the receiverreceives the light conducted from the transmitter through thelight-conducting member, to in this way emit transmission-dependentsignals. Transmission properties are ascertained in this manner, therebyallowing a calibration of the control element. If, moreover, the controlelement has a second light-conducting member whose optical propertiesare in correlation with the light-conducting member of the rain sensor,a simple and nevertheless precise calibration of the deviceadvantageously results.

[0016] Due to the storage of the correlation in the control element as afunctional cohesion, it is possible to store every correlation of theoptical properties of the two subassemblies, rain sensor and controlelement, representable as function.

[0017] The correlation is advantageously also stored in the controlelement as a cohesion in table form, in order to permit a rapidcalibration using as little computing expenditure as possible.

[0018] If the two light conductors of the rain sensor and of the controlelement are constructed in one piece, then a similar change in theoptical properties results, since both are subject to the same exposureof sunlight. This is advantageous since the transmission properties ofplastics are influenced substantially by the ultraviolet radiation towhich they are subject during exposure to sunlight.

[0019] In addition, arranging the electronics of the control element andthe electronics of the rain sensor in one piece on a singleprinted-circuit board saves costs and resources.

[0020] It is also advantageous if the control element is able to becalibrated at time intervals using a calibration parameter which is afunction of the service life of the control element. Aging effects ofthe optical media, or even aging effects of the receiver elements, whichtypically are constructed as semiconductor components, are to a highdegree time-dependent, which means the calibration on the basis of theservice life represents a good first approximation.

[0021] It is also particularly advantageous to be able to calibrate thecontrol element with the aid of a calibration parameter which is afunction of the history of the control element. Since the aging of thecontrol element is accelerated by high irradiating light intensities,the calibration may be carried out, for example, using a calibrationparameter which is calibrated from the sum of the intensities that havepreviously fallen on the control element and been measured.

BRIEF DESCRIPTION OF THE DRAWING

[0022] Exemplary embodiments of the invention are shown in the drawingand are explained in greater detail in the following description.

[0023]FIG. 1 shows a device of the present invention in schematicrepresentation;

[0024]FIG. 2 shows a variation of the device according to the invention;

[0025]FIG. 3 shows method steps of a method of the present invention inschematic representation;

[0026]FIG. 4 shows a further variation of a device according to thepresent invention.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0027]FIG. 1 shows a device of the present invention for the automaticcontrol of illumination devices 24. It has a rain sensor 10 which isable to be calibrated by a calibration module 12.

[0028] Rain sensor 10 functions according to an optical total reflectionmethod. A transmitter 14 sends light through a first light-conductingmember 16 to a window 18, typically the windshield of a motor vehicle.The light penetrates window 18 and is totally reflected at the outsideof window 18, facing away from first light-conducting member 16, at theglass-air interface, provided it is not wet from precipitation. Thereflected light in turn travels from window 18 through firstlight-conducting member 16 to a receiver 20. This receiver 20 thereuponemits signals S, dependent on the light received, to calibration module12.

[0029] To improve the ability to recognize precipitation on the outsideof window 18, calibration module 12 performs a calibration in knowledgeof the light emitted by transmitter 14.

[0030] Control element 22 is used for controlling illumination devices24. The ambient light gets through window 18 and through secondlight-conducting member 26, arriving at a further receiver 28. It isconnected to electronics 30 of control element 22 which evaluates itssignals and, in dependence on them, controls illumination devices 24. Tothat end, stored in electronics 22 are so-called operating points whichin each case correspond to a defined brightness. If the signal offurther receiver 28 exceeds or falls below one or more of theseoperating points, illumination devices 24 are triggered, that is to say,are switched on or off or are dimmed.

[0031] First and second light-conducting members 16, 18 may naturallyalso be constructed in one piece. In the same way, electronics 30 ofcontrol element 22 may be disposed on the same board of calibrationmodule 12, which may also fulfill still further functions.

[0032]FIG. 2 shows a variation of a device according to the presentinvention. In this case, no rain sensor is used for the calibration, butrather a separate calibration section within control element 22. Lightfrom transmitter 14 is transmitted through light-conducting members 16,26 to receiver 20. In knowledge of the transmitted and received light,electronics 30 thereupon performs a calibration. This alters theoperating points stored in electronics 30, or amplifies the signalemitted by further receiver 28.

[0033] In the following, the functioning of the device of the presentinvention, and thus also the method of the present invention, areclarified.

[0034] In a first step 40, rain sensor 10 is activated. Using itstransmitter 14, it thereupon sends light of predetermined intensity inthe direction of window 18, and sees to it that window 18 is clean, i.e.is free of dirt and precipitation. This may be accomplished, forexample, in that the rain sensor drives wiper motor M, and thus carriesout a reference wiping using washer fluid, if desired.

[0035] In a calibration step 42, the light which was totally reflectedat window 18 is detected by receiver 20. It thereupon emits a signal Sto calibration module 12 of rain sensor 10, the calibration module thencarrying out a comparison to a setpoint value which may also betransmitter-dependent. Since at this moment, window 18 is free ofprecipitation and dirt, signal S is determined primarily by thetransparency of window 18 and of first light-conducting member 16,respectively. Because as a rule, window 18 in motor vehicles is made oflaminated glass, signal S represents first and foremost a measure forthe transparency of first light-conducting member 16. In this way, uponeach activation or at other time intervals, which need be neitherconstant nor predetermined, rain sensor 10 is able to be calibrated.

[0036] Calibration parameters K obtained during this calibration step 42are utilized in a third step 44 by control element 22 to shift theoperating points at which, if they are exceeded or not attained,illumination devices 24 are triggered. If, for example, the resultascertained in calibration step 42 yields a transmission of 95percentage of the setpoint value 100 percentage, then the operatingpoints may be lowered by approximately 5 percentage in the result inorder to compensate for the effect of second light conductor 26. Sincefirst light-conducting member 16 and second light-conducting member 26may also be made of different materials which may exhibit differentaging behavior as well, electronics 30 of control element 22 may alsocarry out a correction of the result. This correction is stored ascorrelation in electronics 30, and may be made of a simple factor, oralso of a complex function.

[0037] In a fourth step 46, the device is activated, so that if theoperating points of control element 22 are exceeded or not attained,illumination devices 24 are triggered.

[0038] The ambient light travels through window 18 and secondlight-conducting member 26 to receiver 28. It relays further signals L,obtained therefrom, to electronics 30 which triggers illumination device24 as a function of the operating points.

[0039] For example, the calibration process of control element 22 may becarried out upon each activation of rain sensor 10. Since the opticalproperties of the light conductor change only slowly, this is adequate,given sufficient frequency of precipitation. In principle, however,intervals I and T are completely independent, and therefore do not haveto be either constant or identical. If control element 22 is notconstantly active, rain sensor 10 may also store its last calibrationparameter K, and upon activation of control element 22, may transmit itto it. The specific embodiment shown in FIG. 2 functions according tothe same principle. Since here, however, the light from transmitter 14does not have to be totally reflected at the outside of window 18, theneed for the reference wiping in response to the activation iseliminated.

[0040] In one very simple design as shown in FIG. 4, the opticalproperties of light-conducting member 26 may also be determinedapproximately only from the service life. To that end, electronics 30receives a time or date signal, and in accordance with it, withincreasing age, shifts the operating points to a higher sensitivity. Themagnitude of this shift may be determined, for example, from empiricalvalues or model calculations.

[0041] In a variation, it is also conceivable to provide electronics 30with a summator which totals the quantity of light fallen onlight-conducting member 26 during the history of the control element.Typically, the properties of plastics, and consequently also theirtransmission properties, change due to exposure to sunlight. However,the light irradiation is continually measured by receiver 28, and inthis way, conclusions may be drawn about the transmission properties ofthe light conductor. Using this data, the operating points may then bealtered, and therefore a calibration may be carried out. A memory cellin combination with a capacitor may be used as summator, the memory cellbeing incremented when a defined voltage level is exceeded at theintegrating capacitor, and it is thereupon discharged. In the simplestcase, it is possible to use only a capacitor as summator.

[0042] In principle, a calibration of a control element for theautomatic control of illumination devices 24 may also be achieved inthat, at specific intervals, light of defined intensity and frequency isirradiated through windshield 18 and light-conducting member 26 ontofurther receiver 28, the signal emitted by further receiver 28 beingused by electronics 30 for shifting the operating points. To that end,electronics 30 must be switched into a programming mode which, forexample, may be achieved by a defined pulsed irradiation into receiver28. This defined irradiation may be of a digital nature and correspondto a type of code. Therefore, the entire programming of control element30 may be carried out on the basis of the incident light in furtherreceiver 28, which means no further switching, trimming or connectorelements are necessary on control element 30. If control element 30 hasa plurality of receivers 28, then naturally the most varied combinationsof lighting may also be used for the programming.

[0043] Of course, it is also possible to program the electronics of rainsensor 10 in this manner. cm What is claimed is:

1. A method for the automatic control of illumination devices (24),particularly of a motor vehicle, having a control element (22) whichacts on illumination devices (24) and which is calibrated at timeintervals (T), for which calibration parameters (K) are taken intoaccount by a rain sensor (10) that is likewise calibrated at timeintervals (I).
 2. The method as recited in claim 1, wherein the rainsensor (10) has at least one transmitter (14) radiating light, onereceiver (20) and a first light-conducting member (16); the light isconducted at least from the transmitter (14) via the firstlight-conducting member (16) into the receiver (20); the receiver (20)emits signals (S) as a function of the light received; a setpoint valueis compared to the signals (S); and the rain sensor (10) is calibratedas a function of the result of the comparison.
 3. The method as recitedin claim 2, wherein a transmittance is determined as result from thecomparison, and the control element (22) is calibrated with the aid ofthis transmittance.
 4. The method as recited in claim 2 or 3, whereinthe control element (22) has a second light-conducting member (26), theoptical properties of the second light-conducting member (26) being incorrelation with the transmittance of the first light-conducting member(16), and the correlation being taken into account in the calibration ofthe control element (22).
 5. The method as recited in claim 4, whereinthe calibration is carried out with the aid of a correlation stored as afunctional cohesion in the control element (22).
 6. The method asrecited in claim 4, wherein the calibration is carried out with the aidof a correlation stored as a table in the control element (22).
 7. Amethod for the automatic control of illumination devices (24),particularly of a motor vehicle, having a control element (22) whichacts on illumination devices (24) and which is calibrated at timeintervals (T), for which a calibration parameter (K), that is taken intoaccount in the calibration, is determined over a calibration section(32) at time intervals (I).
 8. A method for the automatic control ofillumination devices (24), particularly of a motor vehicle, having acontrol element (22) which acts on illumination devices (24) and whichis calibrated at time intervals (T), for which a calibration parameter(K), that is a function of the service life of the control element (22),is taken into account in the calibration.
 9. A method for the automaticcontrol of illumination devices (24), particularly of a motor vehicle,having a control element (22) which acts on illumination devices (24)and which is calibrated at time intervals (T), for which a calibrationparameter (K) that is a function of the history of the control element(22) is taken into account in the calibration.
 10. A device for theautomatic control of external illumination devices (24), particularlyfor carrying out a method as recited in one of the preceding claims,comprising a rain sensor (10) having a calibration module (12), whereina control element (22) is provided which calibrates the device with theaid of at least one calibration parameter (K) of the rain sensor (10).11. The device as recited in claim 10, wherein the rain sensor (10) hasat least one transmitter (14) radiating light, a first light-conductingmember (16) and a receiver (20) which receives light from thetransmitter (14) and emits transmission-dependent signals (S) as afunction of this received light; and the calibration module (12) of therain sensor (10) emits at least one result which is a function of thetransmission of the first light-conducting member (16).
 12. The deviceas recited in claim 11, wherein the control element (22) has a furtherreceiver (28) and a second light-conducting member (26) whose opticalproperties are in correlation with the result of the calibration module(12) of the rain sensor (10); and the control element (22) is designedin such a way that it takes the correlation into account in thecalibration of the device.
 13. The device as recited in claim 12,wherein the correlation is stored in the control element (22) as afunctional cohesion.
 14. The device as recited in claim 12, wherein thecorrelation is stored in the control element (22) as a cohesion in tableform.
 15. The device as recited in one of claims 12 through 14, whereinthe first light-conducting member (16) and the second light-conductingmember (26) are constructed in one piece.
 16. The device as recited inclaim 10, wherein the rain sensor (10) and the control element (22) eachhave an electronics (30) which is arranged in one piece, particularly ona single board.
 17. A device for the automatic control of illuminationdevices (24), particularly of a motor vehicle, having a control element(22) controlling illumination devices (24) depending on brightness, thecontrol element being able to be calibrated at time intervals (T) withthe aid of a calibration parameter (K) that is a function of the servicelife of the control element (22).
 18. A device for the automatic controlof illumination devices (24), particularly of a motor vehicle, having acontrol element (22) controlling illumination devices (24) depending onbrightness, the control element being able to be calibrated at timeintervals (T) with the aid of a calibration parameter (K) that is afunction of the history of the control element (22).
 19. The device asrecited in claim 18, wherein the history is determined as the sum ofprevious measured values of brightness.